1. Field of the Invention
This invention relates to connectors such as bearings, and more particularly to a maintenance free connector having a roller with an integral lubricious wear layer/metallic substrate combination.
2. Background Information
Throughout this application, various publications, patents and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure.
Maintenance-free sliding bearings comprising a metal substrate and a plastic bearing layer are known. Such bearings provide convenient means for rotatably, pivotably or slidably fastening multiple members to one another in a maintenance free manner. Applications for such bearings include those that utilize continuous rotational movement such as journals for supporting a driven shaft. These bearings are also suitable for applications that employ repeated pivotal movement such as automotive door hinges, door checks, brake and accelerator pedals. Additional applications include those that utilize repeated reciprocal movement such as shock absorbers for automobiles, motorcycles and bicycles, and automotive struts. These bearings may also be used in lighter duty applications such as multiple bar linkages commonly utilized in the automotive industry for trunk deck lid and hood hinges. Such maintenance free bearings may comprise a variety of configurations, such as, for example, bushes or journal bearings, thrust bearings or washers, locating pads, valve port plates, and wearing members for a variety of mechanisms.
An example of such a bearing is sold under the “Norglide®” designation, available from Norton Performance Plastics Corporation, of Wayne N.J. Norglide comprises a thin sheet of bearing material, such as, for example, a PTFE (polytetrafluoroethylene) compound, bonded onto a metallic backing using high temperature thermoplastic films, (e.g. PFA and ETFE) heat and pressure, as described in U.S. Pat. No. 5,573,846 entitled “Polyfluorocarbon Coated Metal Bearing” which is hereby incorporated by reference herein.
One variety of Norglide® materials available from Norton is known as the “Norglide® M” bearings. Norglide M bearings are substantially similar to Norglide materials as discussed above, but they utilize a bearing layer having an open-mesh metal fabric reinforcement disposed therein.
Additional examples of bearings of this general type are disclosed in commonly assigned U.S. Pat. No. 5,860,780, entitled “Self-Lubricated Thrust Rivet”; and U.S. patent application Ser. No. 08/899,572, entitled “Self-Lubricated Bearing” which are both incorporated by reference herein.
Other self-lubricated bearings include a “DU” bearing available from The Glacier Metal Company Limited, Argule House, Joel Street, Northwood Hills, Middlesex HA6 1LN, England. The DU bearing consists of a composite material in which a porous bronze layer is bonded to a metal backing. The porous bronze layer is impregnated with a polymer such as PTFE with a top layer or lining of polymer disposed thereon.
As mentioned above, these bearings are fabricated by applying the lubricious bearing layer to a substantially flat (planar) substrate and subsequently forming the laminate into desired geometries, such as cylindrical bushes, rivets, etc. The thickness of the substrate sheets may be varied, depending on the structural requirements of the particular application. However, increasing the substrate thickness tends to increase the difficulty of forming the resulting laminate, to increase the minimum radius to which the laminate may be formed. For this reason, most self-lubricated bearings discussed hereinabove utilize relatively thin substrates, i.e. having a thickness on the order of about 0.2–2 mm.
For heavier duty applications, in which the increased structural characteristics of a thicker substrate is desired, conventional bearing fabrication techniques have included individually forming the substrate and/or self-lubricating layers as discrete members, followed by assembly of the two discrete parts to one another. For example, U.S. Pat. No. 5,236,784, entitled “Bearing Material and Plastic Bearing” discloses pre-forming a tubular metallic cylinder in a conventional manner, and subsequently molding a plastic bearing material to an inner surface of the cylinder to form a completed bearing member. Conversely, U.S. Pat. No. 5,806,985, entitled “Rod Guide and Method For Its Manufacture” discloses fabricating a tubular bush from PTFE and separately fabricating a discrete metallic carrier having an inner cylindrical surface with a greater diameter than the outer diameter of the bush. The bush is subsequently assembled concentrically with the carrier and secured in place with a die-casting material such as zinc.
Although these approaches of forming (shaping) one or more of the members prior to assembly approaches may operate satisfactorily in some applications, they are not without disadvantages. For example, it is generally more difficult to form an adequate bond between the plastic layer and the substrate than in many of the aforementioned laminated bearings due to the difficulty of applying as much heat and pressure to cylindrical layers as may be applied to planar laminates. Thus, these discretely formed bearings may experience reduced life and/or be more expensive to manufacture than the sheet laminated bearings.
Thus, a need exists for an improved maintenance free bearing that addresses the problems of the prior art.